<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        a {
            text-decoration: none;
            color: #000000;
        }
        
        .login-header {
            width: 100%;
            text-align: center;
            height: 30px;
            font-size: 24px;
            line-height: 30px;
        }
        
        .login {
            display: none;
            width: 512px;
            height: 280px;
            position: fixed;
            border: #ebebeb solid 1px;
            left: 50%;
            top: 50%;
            background-color: #ffffff;
            box-shadow: 0px 0px 20px #ddd;
            z-index: 9999;
            transform: translate(-50%, -50%);
        }
        
        .login-title {
            position: relative;
            width: 100%;
            margin-top: 10px;
            text-align: center;
            height: 40px;
            line-height: 40px;
            cursor: move;
            font-size: 18px;
        }
        
        .login-input-content {
            margin-top: 20px;
        }
        
        .login-bg {
            display: none;
            width: 100%;
            height: 100%;
            position: fixed;
            top: 0px;
            left: 0px;
            background: rgba(0, 0, 0, .3);
        }
        
        .login-input {
            padding-left: 10px;
        }
        
        .login-input input {
            height: 35px;
            width: 350px;
            line-height: 35px;
            border: #ebebeb 1px solid;
            text-indent: 5px;
            padding-left: 10px;
            margin-bottom: 10px;
        }
        
        .login-input label {
            float: left;
            width: 90px;
            padding-right: 10px;
            text-align: right;
            line-height: 35px;
            height: 35px;
            font-size: 14px;
        }
        
        .login-title span {
            position: absolute;
            font-size: 12px;
            right: -20px;
            top: -30px;
            background: #ffffff;
            border: #ebebeb solid 1px;
            width: 40px;
            height: 40px;
            border-radius: 20px;
        }
        
        .login-button {
            width: 50%;
            margin: 30px auto 0px auto;
            line-height: 40px;
            font-size: 14px;
            border: #ebebeb 1px solid;
            text-align: center;
        }
    </style>
</head>

<body>
    <div class="login-header">
        <a href="javascript:;" id="link">点击弹出登录框</a>
    </div>
    <div class="login">
        <div class="login-title" id="title">登录会员
            <span><a href="javascript:;"id="closeBtn">关闭</a></span>
        </div>
        <div class="login-input-content">
            <div class="login-input">
                <label>用户名:</label>
                <input type="text" placeholder="请输入用户名" value="">
            </div>
            <div class="login-input">
                <label>登录密码:</label>
                <input type="password" placeholder="请输入登录密码" name="" id="">
            </div>
        </div>
        <div class="login-button"><a href="javascript:;">登录会员</a></div>
    </div>
    <div class="login-bg"></div>
    <script>
        var login = document.querySelector(".login");
        var bg = document.querySelector(".login-bg");
        var link = document.querySelector("#link");
        var closeBtn = document.querySelector("#closeBtn");
        var title = document.querySelector('#title');
        //点击弹出登录框
        link.addEventListener("click", function() {
                bg.style.display = "block";
                login.style.display = "block";
            })
            //点击closeBtn 关闭登录框
        closeBtn.addEventListener("click", function() {
                bg.style.display = "none";
                login.style.display = "none";
            })
            //拖拽
        title.addEventListener("mousedown", function(e) {
            var x = e.pageX - login.offsetLeft;
            var y = e.pageY - login.offsetTop;
            document.addEventListener("mousemove", move);

            function move(e) {
                login.style.left = e.pageX - x + "px";
                login.style.top = e.pageY - y + 'px';
            }
            document.addEventListener('mouseup', function() {
                document.removeEventListener('mousemove', move);
            })
        })
    </script>
</body>

</html>